encoderm.m
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- function en_output = encoderm( x, g, alpha, puncture )
- % Copyright Nov. 1998 Yufei Wu
- % MPRG lab, Virginia Tech.
- % for academic use only
- % uses interleaver map 'alpha'
- % if puncture = 1, unpunctured, produces a rate 1/3 output of fixed length
- % if puncture = 0, punctured, produces a rate 1/2 output
- % multiplexer chooses odd check bits from RSC1
- % and even check bits from RSC2
- % determine the constraint length (K), memory (m)
- % and number of information bits plus tail bits.
- [n,K] = size(g);
- m = K - 1;
- L_info = length(x);
- L_total = L_info + m;
- % generate the codeword corresponding to the 1st RSC coder
- % end = 1, perfectly terminated;
- input = x;
- output1 = rsc_encode(g,input,1);
- % make a matrix with first row corresponing to info sequence
- % second row corresponsing to RSC #1's check bits.
- % third row corresponsing to RSC #2's check bits.
- y(1,:) = output1(1:2:2*L_total);
- y(2,:) = output1(2:2:2*L_total);
- % interleave input to second encoder
- for i = 1:L_total
- input1(1,i) = y(1,alpha(i));
- end
- output2 = rsc_encode(g, input1(1,1:L_total), -1 );
- y(3,:) = output2(2:2:2*L_total);
- % paralell to serial multiplex to get output vector
- % puncture = 0: rate increase from 1/3 to 1/2;
- % puncture = 1; unpunctured, rate = 1/3;
- if puncture > 0 % unpunctured
- for i = 1:L_total
- for j = 1:3
- en_output(1,3*(i-1)+j) = y(j,i);
- end
- end
- else % punctured into rate 1/2
- for i=1:L_total
- en_output(1,n*(i-1)+1) = y(1,i);
- if rem(i,2)
- % odd check bits from RSC1
- en_output(1,n*i) = y(2,i);
- else
- % even check bits from RSC2
- en_output(1,n*i) = y(3,i);
- end
- end
- end
- % antipodal modulation: +1/-1
- en_output = 2 * en_output - ones(size(en_output));